TRANSMISSION WHEEL.--In Fig. 32 is shown a section of the differential housing, 1, in which, for convenience, all refinements of construction are eliminated. This shows the divided axle shafts 5, 6. In Fig. 33 is shown a side view of the same housing. This may be connected with the motor shaft by means of bevel gears, or driven by a sprocket chain. In either case the housing 1 is the substitute for the thrust bar B, in Fig. 28, and the bevel pinions 2, which are mounted within the wheel 1, represent the equalizer bar of that figure. [Illustration: Fig. 31. Differential in Housing.] The gears which make up the train are usually put into a suitable casing, as illustrated in Fig. 31, which gives a good example of the construction. The housing A is fixed to the side of a large bevel gear B, this gear being designed to receive power from the motor through a bevel pinion C. One part of the axle D passes through the gear B, and is fixed to a bevel gear E within the housing, and the other part of the axle F passes through the housing and is fixed to a bevel gear G, the same size as gear E. Intermediate the two gears is a pair of bevel pinions H, H, and these latter are mounted on pivots I, I, projecting inwardly from the housing. The fact that the pinions are attached to housing has the effect of complicating the matter, so that it may be well to show the relative arrangement of the gears without the housing. [Illustration: Fig. 32. Section of Differential.] [Illustration: Fig. 33. Side View of Differential Wheel.] In Fig. 34 we have added to Fig. 33, two bevel gears 3, 4, which are mounted on the axles 5, 6, these representing the rear drive axles of the car. ACTION OF TRANSMISSION GEARING.--From the foregoing it will be seen that the axles abut each other, within the hub of the large gear 1, within which they are journaled. We might, therefore, call these pinions the counterparts of the bars E E. [Illustration: Fig. 34. Top View of Differential Wheel.] As long as the resistance to the turning movements of the pinions 3, 4 is the same, the housing through pinions 2, 2, will simply carry the bevel gears 3, 4 around with it, without turning them, just the same as the equalizer bar B was moved forward without either end swinging back or forth; but the moment the wheel of the shaft 5, for instance, is compelled to travel at a higher rate of speed, or the wheel on shaft 6 meets with a greater resistance, the small equalizing gears 2 will turn, and the revoluble motion of the housing 1, while transmitting the power, and also carrying the gears, will act, in effect, the same as the push bar shown in the previous illustration. Like the equalizing bar, the effect is to turn one wheel, say 3, with less, and the other wheel 4 with more than the normal power or speed.